What adjuvant therapy and surveillance strategy are recommended for a 60‑year‑old man with stage IIA (pT4a N0 M0) mucinous adenocarcinoma of the cecum/ileocecal junction after right hemicolectomy?

Management of Stage IIA (pT4a N0 M0) Mucinous Adenocarcinoma of the Cecum After Right Hemicolectomy

This patient should be offered adjuvant chemotherapy with FOLFOX (oxaliplatin plus 5-fluorouracil/leucovorin) for 6 months, given the T4a stage and mucinous histology, both of which represent high-risk features in stage II colon cancer.

Adjuvant Chemotherapy Decision

High-Risk Stage II Features Present

This patient has multiple high-risk features that warrant consideration of adjuvant chemotherapy:

• T4a tumor (invasion through muscularis propria into pericolic tissue with mucin pools reaching serosa) is a well-established high-risk feature 1, 2, 3
• Mucinous histology is associated with poorer prognosis in locally advanced colorectal cancer treated with adjuvant chemotherapy 4
• Elevated preoperative CEA (10.2 ng/mL) is another high-risk indicator 3

While adjuvant chemotherapy is not routinely recommended for all stage II colon cancer, patients with high-risk features including T4 tumors should be strongly considered for treatment 1, 2, 3.

MMR Status Consideration

The patient's tumor is MMR proficient (MSS), which supports the use of adjuvant chemotherapy. Patients with deficient MMR (dMMR) stage II disease have excellent prognosis and do not benefit from 5-fluorouracil-based therapy 5. However, this patient's MMR-proficient status means he is likely to benefit from standard fluoropyrimidine-based chemotherapy 5.

Recommended Chemotherapy Regimen

FOLFOX (oxaliplatin 85 mg/m² on day 1 plus leucovorin 200 mg/m² and 5-fluorouracil 400 mg/m² bolus followed by 600 mg/m² 22-hour infusion on days 1 and 2, every 2 weeks for 12 cycles/6 months) is the recommended regimen 2, 6.

• The MOSAIC trial demonstrated that FOLFOX significantly improves disease-free survival in stage II and III colon cancer 6
• For high-risk stage II patients, FOLFOX provides approximately 15% improvement in disease-free survival 2
• Alternative regimen: CAPOX (capecitabine plus oxaliplatin) can be used with similar efficacy 2

Duration of Treatment

Standard duration is 6 months (12 cycles of FOLFOX) 2, 6. While the IDEA study suggested 3 months may be considered for certain low-risk patients, this patient's T4a stage and mucinous histology place him in a higher-risk category warranting full 6-month treatment 2.

Important Caveats Regarding Mucinous Histology

Mucinous adenocarcinoma has distinct biological behavior that impacts prognosis:

• Mucinous histology is associated with significantly poorer disease-free survival (HR 2.95) and overall survival (HR 1.23) in patients receiving first-line adjuvant chemotherapy compared to non-mucinous adenocarcinoma 4
• This poorer prognosis with mucinous histology persists even in stage III disease and with FOLFOX regimens 4
• The adequacy of right hemicolectomy for mucinous tumors is appropriate, as more extensive resection does not improve outcomes 7

Surveillance Strategy

Post-Treatment Monitoring Schedule

Implement intensive surveillance given the high-risk features:

• CEA monitoring: Every 3 months for 2 years, then every 6 months for years 3-5 1, 3
• CT chest/abdomen/pelvis: Every 3-6 months for 2 years, then every 6-12 months up to 5 years total 1, 3
• Colonoscopy: At 1 year post-surgery (since preoperative colonoscopy was completed), then every 3-5 years thereafter 1, 3

Rationale for Intensive Surveillance

The T4a stage places this patient at higher risk for recurrence that may be amenable to salvage surgery 3. Regular imaging is essential to detect potentially resectable recurrences, particularly hepatic or pulmonary metastases 1.

Toxicity Monitoring During Chemotherapy

Key toxicities to monitor with FOLFOX include:

• Peripheral neuropathy: Occurs in approximately 12.4% during treatment, though decreases to 1.1% at 1-year follow-up 2, 6
• Neutropenia and myelosuppression 2, 6
• Gastrointestinal toxicity (diarrhea, nausea) 2

Consider dose modifications or early discontinuation of oxaliplatin if severe neuropathy develops, as fluoropyrimidine monotherapy may still provide benefit 5.

Critical Pitfalls to Avoid

• Do not withhold chemotherapy based solely on stage II designation – this patient has clear high-risk features (T4a, mucinous histology, elevated CEA) that justify treatment 1, 2, 3
• Do not use bevacizumab, cetuximab, panitumumab, or irinotecan in the adjuvant setting – these are not recommended outside clinical trials 5
• Adequate lymph node examination was performed (36 nodes examined, all negative), which confirms accurate staging and supports the treatment decision 1, 3